Shadows of Forgotten Ancestors

Shortly, we will sharpen our focus to one world only, the Earth. We will examine the evolution of its atmosphere, surface, and interior, and the steps that led to life and animals and us. Our focus will then progressively narrow, and it will be easy to think of us as isolated from the Cosmos, a self-sufficient world minding its own business. In fact, the history and fate of our planet and the beings upon it have been profoundly, crucially influenced, through the whole history of the Earth and not just in the time of its origins, by what’s out there. Our oceans, our climate, the building blocks of life, biological mutation, massive extinctions of species, the pace and timing of the evolution of life, all cannot be understood if we imagine the Earth hermetically sealed from the rest of the Universe, with only a little sunlight trickling in from the outside.

The matter that makes up our world came together in the skies. Enormous quantities of organic matter fell to Earth, or were generated by sunlight, setting the stage for the origin of life. Once begun, life mutated and adapted to a changing environment, partially driven by radiation and collisions from outside. Today, nearly all life on Earth runs off energy harvested from the nearest star. Out there and down here are not separate compartments. Indeed, every atom that is down here was once out there.⁵

Not all of our ancestors made the same sharp distinction we do between the Earth and the sky. Some recognized the connection. The grandparents of the Olympian gods and therefore the ancestors of humans were, in the myths of the ancient Greeks, Uranus,⁶ god of the sky, and his wife Gaia, goddess of the Earth. Ancient Mesopotamian religions had the same idea. In dynastic Egypt the gender roles were reversed: Nut was goddess of the sky, and Geb god of Earth. The chief gods of the Konyak Nagas on the Himalayan frontier of India today are called Gawang, “Earth-Sky,” and Zangban, “Sky-Earth.” The Quiché Maya (of what is now Mexico and Guatemala) called the Universe cahuleu, literally “Sky-Earth.”

That’s where we live. That’s where we come from. The sky and the Earth are one.

Chapter 2

SNOWFLAKES FALLEN ON THE HEARTH

There is not yet one person, one animal, bird, fish, crab, tree, rock, hollow, canyon, meadow, forest. Only the sky alone is there …

Popol Vuh: The Mayan Book of the Dawn of Life¹

Before the High and Far-Off Times, O my Best Beloved, came the Time of the Very Beginnings; and that was in the days when the Eldest Magician was getting Things ready. First he got the Earth ready; then he got the Sea ready; and then he told all the Animals that they could come out and play.

RUDYARD KIPLING

“The Crab That Played with the Sea”²

If you could drive an automobile straight down, in an hour or two you would find yourself deep inside the upper mantle of the Earth, far beneath the pediments of the continents, approaching an infernal region where the rock becomes a viscous liquid, mobile and red-hot. And if you could drive for an hour straight up, you would find yourself in the near-vacuum of interplanetary space.³ Beneath you—blue, white, breathtakingly vast, and brimming over with life—would stretch the lovely planet on which our species and so many others have grown up. We inhabit a shallow zone of environmental clemency. Compared to the size of the Earth, it is thinner than the coat of shellac on a large schoolroom globe. But earlier, long ago, even this narrow habitable boundary between hell and heaven was unready to receive life.

——

The Earth accumulates in the dark. Although the primitive Sun is ablaze, there is so much gas and dust between the Earth and the Sun that at first no light gets through. The Earth is embedded in a black cocoon of interplanetary debris. There’s an occasional flash of lightning by which you glimpse a ravaged, pockmarked, not quite spherical world. As it gathers up more and more matter, in units ranging from dust to worldlets, it becomes rounder, less lumpy.

A collision with a hurtling worldlet produces a shattering explosion, and excavates a great crater. Much of the impactor disintegrates into powder and atoms. There are vast numbers of such collisions. Ice is converted to steam. The planet is blanketed in vapor—which holds in the heat from the impacts. The temperature rises until the Earth’s surface becomes entirely molten, a roiling world-ocean of lava, glowing by its own red heat, and surmounted by a stifling atmosphere of steam. These are the final stages of the great gathering in.

In this epoch, when the Earth is new, the most spectacular catastrophe in the history of our planet occurs: a collision with a sizeable world. It does not quite crack the Earth open, but it does blast a good fraction of it out into nearby space. The resulting ring of orbiting debris shortly falls together to become the Moon.